From politics to pop culture, the Church of Latter-day Saints is now a mainstream force. But the church's high-stakes campaign against gay marriage has made it a target. A look at what Mormons believe

Last November, Jay Pimentel began hearing that people in his neighborhood were receiving letters about him. Pimentel lives in Alameda, Calif., a small, liberal-leaning community hanging off Oakland into the San Francisco Bay. Pimentel, who is a Mormon, had supported Proposition 8, the ballot initiative banning same-sex marriage. And that made him a target. "Dear Neighbor," the letter began, "Our neighbors, Colleen and Jay Pimentel"  and it gave their address  "contributed $1,500.00 to the Yes on Proposition 8 campaign. NEIGHBORS SHOULD BE AWARE OF THEIR NEIGHBORS' CHOICES." The note accused the Pimentels of "obsessing about same-sex marriage." It listed...